/*
 * Copyright (c) 2007-2012, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */
package com.sun.org.apache.bcel.internal.generic;

/* ====================================================================
 * The Apache Software License, Version 1.1
 *
 * Copyright (c) 2001 The Apache Software Foundation.  All rights
 * reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The end-user documentation included with the redistribution,
 *    if any, must include the following acknowledgment:
 *       "This product includes software developed by the
 *        Apache Software Foundation (http://www.apache.org/)."
 *    Alternately, this acknowledgment may appear in the software itself,
 *    if and wherever such third-party acknowledgments normally appear.
 *
 * 4. The names "Apache" and "Apache Software Foundation" and
 *    "Apache BCEL" must not be used to endorse or promote products
 *    derived from this software without prior written permission. For
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 *
 * 5. Products derived from this software may not be called "Apache",
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 *    prior written permission of the Apache Software Foundation.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation.  For more
 * information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 */
import java.io.*;
import com.sun.org.apache.bcel.internal.util.ByteSequence;
import com.sun.org.apache.bcel.internal.classfile.Utility;
import com.sun.org.apache.bcel.internal.Constants;

/**
 * Abstract super class for instructions dealing with local variables.
 *
 * @author  <A HREF="mailto:markus.dahm@berlin.de">M. Dahm</A>
 */
public abstract class LocalVariableInstruction extends Instruction implements TypedInstruction, IndexedInstruction {
    protected int n = -1; // index of referenced variable
    private short c_tag = -1; // compact version, such as ILOAD_0
    private short canon_tag = -1; // canonical tag such as ILOAD

    private final boolean wide() {
        return n > Constants.MAX_BYTE;
    }

    /**
     * Empty constructor needed for the Class.newInstance() statement in
     * Instruction.readInstruction(). Not to be used otherwise.
     * tag and length are defined in readInstruction and initFromFile, respectively.
     */
    LocalVariableInstruction(short canon_tag, short c_tag) {
        super();
        this.canon_tag = canon_tag;
        this.c_tag = c_tag;
    }

    /**
     * Empty constructor needed for the Class.newInstance() statement in
     * Instruction.readInstruction(). Also used by IINC()!
     */
    LocalVariableInstruction() {
    }

    /**
     * @param opcode Instruction opcode
     * @param c_tag Instruction number for compact version, ALOAD_0, e.g.
     * @param n local variable index (unsigned short)
     */
    protected LocalVariableInstruction(short opcode, short c_tag, int n) {
        super(opcode, (short) 2);

        this.c_tag = c_tag;
        canon_tag = opcode;

        setIndex(n);
    }

    /**
     * Dump instruction as byte code to stream out.
     * @param out Output stream
     */
    public void dump(DataOutputStream out) throws IOException {
        if (wide()) // Need WIDE prefix ?
            out.writeByte(Constants.WIDE);

        out.writeByte(opcode);

        if (length > 1) { // Otherwise ILOAD_n, instruction, e.g.
            if (wide())
                out.writeShort(n);
            else
                out.writeByte(n);
        }
    }

    /**
     * Long output format:
     *
     * &lt;name of opcode&gt; "["&lt;opcode number&gt;"]"
     * "("&lt;length of instruction&gt;")" "&lt;"&lt; local variable index&gt;"&gt;"
     *
     * @param verbose long/short format switch
     * @return mnemonic for instruction
     */
    public String toString(boolean verbose) {
        if (((opcode >= Constants.ILOAD_0) && (opcode <= Constants.ALOAD_3)) || ((opcode >= Constants.ISTORE_0) && (opcode <= Constants.ASTORE_3)))
            return super.toString(verbose);
        else
            return super.toString(verbose) + " " + n;
    }

    /**
     * Read needed data (e.g. index) from file.
     * PRE: (ILOAD <= tag <= ALOAD_3) || (ISTORE <= tag <= ASTORE_3)
     */
    protected void initFromFile(ByteSequence bytes, boolean wide) throws IOException {
        if (wide) {
            n = bytes.readUnsignedShort();
            length = 4;
        } else if (((opcode >= Constants.ILOAD) && (opcode <= Constants.ALOAD)) || ((opcode >= Constants.ISTORE) && (opcode <= Constants.ASTORE))) {
            n = bytes.readUnsignedByte();
            length = 2;
        } else if (opcode <= Constants.ALOAD_3) { // compact load instruction such as ILOAD_2
            n = (opcode - Constants.ILOAD_0) % 4;
            length = 1;
        } else { // Assert ISTORE_0 <= tag <= ASTORE_3
            n = (opcode - Constants.ISTORE_0) % 4;
            length = 1;
        }
    }

    /**
     * @return local variable index  referred by this instruction.
     */
    public final int getIndex() {
        return n;
    }

    /**
     * Set the local variable index
     */
    public void setIndex(int n) {
        if ((n < 0) || (n > Constants.MAX_SHORT))
            throw new ClassGenException("Illegal value: " + n);

        this.n = n;

        if (n >= 0 && n <= 3) { // Use more compact instruction xLOAD_n
            opcode = (short) (c_tag + n);
            length = 1;
        } else {
            opcode = canon_tag;

            if (wide()) // Need WIDE prefix ?
                length = 4;
            else
                length = 2;
        }
    }

    /** @return canonical tag for instruction, e.g., ALOAD for ALOAD_0
     */
    public short getCanonicalTag() {
        return canon_tag;
    }

    /**
     * Returns the type associated with the instruction -
     * in case of ALOAD or ASTORE Type.OBJECT is returned.
     * This is just a bit incorrect, because ALOAD and ASTORE
     * may work on every ReferenceType (including Type.NULL) and
     * ASTORE may even work on a ReturnaddressType .
     * @return type associated with the instruction
     */
    public Type getType(ConstantPoolGen cp) {
        switch (canon_tag) {
            case Constants.ILOAD:
            case Constants.ISTORE:
                return Type.INT;
            case Constants.LLOAD:
            case Constants.LSTORE:
                return Type.LONG;
            case Constants.DLOAD:
            case Constants.DSTORE:
                return Type.DOUBLE;
            case Constants.FLOAD:
            case Constants.FSTORE:
                return Type.FLOAT;
            case Constants.ALOAD:
            case Constants.ASTORE:
                return Type.OBJECT;

            default:
                throw new ClassGenException("Oops: unknown case in switch" + canon_tag);
        }
    }
}
